Recent investigations have confirmed the existence of potent reflexes controlling arterial blood pressure in snakes. The physiological mechanisms involved appear similar to those in mammals, but we have yet to assess the components and integrative functions of these control systems in snakes or other reptiles. Because of their morphology and habits, snakes are nearly ideal models for studies of blood pressure control. It is proposed that further research be conducted with the aim of identifying mechanisms controlling arterial pressure and regional perfusion in snakes, especially with regard to the participation of pressure-sensitive reflexes. The approach will encompass quantitative studies of arterial hemodynamics, structural proxerties of the circulation, pharmacology, and the neurophysiology of reflexogenic areas involved with cardiovascular reflexes. Experiments will examine the effects of tilting, blood volume changes, temperature and ventilatory state on arterial pressure, central shunting mechanisms and regional blood flow. Functional baroreceptor mechanisms will be defined in relation to direct and physiological stimulation of potential pressure-sensitive sites on the arterial side of the circulation. Comparative morphological studies will examine structural correlates of arterial pressure regulation in different species of snake which differ in their regulatory capabilities. Among snake species there is considerable adaptive variability of absolute pressure, pressure regulatory capability, and cardiovascular morphology. Physiological and morphological investigations with respect to this variability should provide important information regarding cardiovascular adaptation. These research investigations represent the first comprehensive effort toward understanding the mechanisms and significance of arterial pressure regulation in reptiles. Snakes provide illuminating examples of cardiovascular adaptation and possibly will become recognized as model animals for studies of cardiovascular reflexes.